The present invention relates to a new configuration for the dimples on a golf ball surface which improves the aerodynamic characteristics of the ball.
According to the United States Golf Association (U.S.G.A.) Rules, a golf ball may not have a weight in excess of 1.620 ounces or a diameter smaller than 1.680 inches. The initial velocity of balls conforming to U.S.G.A. regulations may not exceed 250 feet per second with a maximum tolerance of 2%. Initial velocity is measured on a standard machine kept by the U.S.G.A. A projection on a wheel rotating at a defined speed hits the test ball, and the length of time it takes the ball to traverse a set distance after impact is measured. U.S.G.A. regulations also require that a ball not travel a distance greater than 280 yards when hit by the U.S.G.A. outdoor driving machine under specifies conditions. In addition to this specification, there is a tolerance of plus 4% and a 2% tolerance for test error.
These specifications limit how far a struck golf ball will travel in several ways. Increasing the weight of a golf ball tends to increase the distance it will travel and lower the trajectory. A ball having greater momentum is better able to overcome drag. Reducing the diameter of the ball also has the effect of increasing the distance it will travel when hit. This is believed to occur primarily because a smaller ball has a smaller projected area and thus, a lower drag when traveling through the air. Increasing initial velocity increases the distance the ball will travel.
Drag on a golf ball is also reduced by forming a plurality of dimples, often circular, in the outer surface of the ball. The dimples serve to reduce the pressure differential between the front and rear of the ball as it travels through the air.
Current golf ball patterns use various numbers of dimples having specific widths, usually laid out with the goal of maximizing surface coverage as long as symmetry in flight is maintained. Dimple depth is manipulated slightly to achieve a higher or lower trajectory, but the ratio of depth to width is constant on a golf ball at about 7%.
It is known in the patented prior art to provide a golf ball with two groups of dimples having the same diameter but two different depths as disclosed in the U.S. Pat. No. 5,518,246 to Moriyama. It is also known in the patented prior art to provide a golf ball having at least three sets of dimples wherein each of the sets of dimples has a different diameter and depth as disclosed in the Yamagishi U.S. Pat. No. 5,033,750. The ratio of the diameter to depth of the dimples of a particular set is approximately equal to the diameter to depth ratios of the other two sets.
The present invention was developed in order to provide a golf ball having a plurality of dimples of different depths wherein the different-depth dimples are arranged in a particular geometry having a dimple depth progression to improve the aerodynamic characteristics of the ball.
Accordingly, it is a primary object of the invention to provide a golf ball having a spherical surface and including a geometric pattern defined on the golf ball surface. Within the geometries of the pattern are provided a plurality of dimples comprising at least two groups. The first group of dimples has a first depth and the dimples thereof are arranged adjacent to a portion of the perimeter of the each geometry, and the second group of dimples has a second depth different from the first depth. The dimples of the second group are arranged within the first group of dimples. The first and second depths are independent of the widths of the dimples of the first and second groups. Owing to this arrangement of different depth dimples, the golf ball has improved aerodynamic properties.
According to another object of the invention, the golf ball includes a third group of dimples having a third depth different from the second depth and independent of the width of the third group of dimples. The third group of dimples is arranged within the second group of dimples so that a depth progression of dimples is provided within each geometry. In one embodiment, the first group of outer dimples has a greater depth than the second group which in turn has a greater depth than the innermost third group of dimples. In an alternative embodiment, the third group of innermost dimples has a greater depth than the second group which in turn has a greater depth than the outermost first group of dimples. In still another embodiment, the first and third groups of dimples have the same depth which is different from that of the second group of dimples.
It is yet another object of the invention to provide a number of great circles on the surface of the golf ball to define the geometric pattern which comprises a plurality of generally equal triangles. One of the great circles defines the equator of the ball and divides the ball into two hemispheres. The same number of triangles is thus provided in each hemisphere.